Collisions are a source of inefficiency in contention-based MAC protocols
that should be reduced to a minimum. We show that concurrent multiple access
to a communication channel will, however, not necessarily lead to a collision
with undesirable effects. Rather, we demonstrate that it is possible for a
receiver to hear the bitwise "or" of the transmissions of multiple
synchronized senders within communication range. This unconventional
communication model allows the efficient implementation of a number of basic
operations that serve as a foundation for BitMAC: a deterministic,
collision-free, and robust MAC protocol that is tailored to dense sensor
networks, where nodes report sensory data over multiple hops to a sink.